My house has a fusebox. This is a first for me, I've always lived in places with circuit breakers before this.
So, this leads to questions:
- Is there a good reason to replace the fusebox with a circuit breaker ("consumer unit") - convenience seems like the obvious answer - but I don't want to do it just because its unfamiliar to me
- Is this something that one might remotely consider doing oneself or is it just too dangerous to attempt?
- Is there a good www guide to UK electrical code relevant for DIY- ers?
There will no doubt be many answers to this question, but having been through this very matter recently, I will jump in first with my pennyworth.
My reason for changing was that I am on a two cable and local earth supply (there is a proper TLA for this but I can't remember it ! ). My understanding is that this system has the weakness that the earth resistance is high which can be overcome with an RCD. In fact I've now protected both the house and all the out buildings with RCD covered distribution boards and I've put in additional earth rods too. That was my particular reason for doing the change.
Aim for a split distribution board so that the lighting circuits don't go down if a fault trips the RCD. Ironically we had a number of trips to begin with which I traced to the LV under worktop lights.
Doing the replacement is quite straightforward if you are comfortable working with wiring, but you will have to pull the company fuse - I don't know whether you will get charged for this. I was lucky in that our area supply was switched off one day and my only concern was that the supply would come on while I was re-setting the tails.
MCBs and fuses both have minor pros and cons safetywise, there's no clear winner overall. The one area MCBs win is when in the hands of irresponsible people eg tenants.
The big question is as Rob raised, do you have a local earth rod, and do you hahve an RCD or ELCB? If the answers are yes then no, then yes theres a good reason to replace it, but otherwise there isnt.
If you do replce it, check out the RCD RCBO and CU sections here:
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use fuses rather than MCBs for lighting circuits, explained here:
On 1 Feb 2007 12:08:09 -0800 someone who may be snipped-for-privacy@gmail.com wrote this:-
What sort of fuses? Rewirable fuses or cartridge fuses.
What sort of circuit breakers in your previous places?
What sort of circuit breaker? One designed to operate at on a current/time characteristic (a miniature circuit breaker or MCB) or one designed to operate at a certain current inbalance between conductors (a residual current device or RCD)?
A consumer unit is a box in which there are various components. Fuses or MCBs are two sorts of component that may be put in one.
As others have said there are advantages and disadvantages to all types of protective device.
Very sensible.
Which country are you living in? If it is England or Wales then the Labour Party have made it rather difficult. I have no idea about Northern Ireland. In Scotland the position is in some ways easier and in some ways more difficult, depending on the precise circumstances.
Referring to a "code" indicates that you need to brush up on UK wiring practice before doing anything.
First you need to distinguish the types of fuse you refer to. Two types are common: re-wireable and cartridge fuses. The re-wireable ones are the least desirable since they are firstly open to abuse (can easily be rewired with the wrong rating of wire etc), and their tripping characteristics are not as good in certain types of fault scenario. They are also much more fiddly to replace when huddled in an under stair cupboard in the dark with a torch!
Cartridge fuses on the other hand have very few of the downsides of rewireable fuses, and in some cases are preferable to MCBs (they usually offer the ability to break higher fault currents).
MCBs have two tripping mechanisms - a thermal one designed to clear sustained overloads, and a magnetic one designed to clear high current fault conditions. This can work both for and against you since they are more "twitchy" to very short duration fault currents. Good if it is a genuine fault you are clearing, but also more likely to trip when a bulb blows etc. (although conversely they are easy to reset)
So the answer to your question is not just a technical one, but needs to take into account the likely users.
Like many things it is not at all dangerous, *if* you know what you are doing!
However, the question you ask is perhaps deeper that you anticipate in that there is plenty of detail that you need to understand to be able to do the work safely. Knowing what type of earthing system you have is a fundamental consideration for example:
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will have a big effect on the design of system you would install. How you would configure your RCDs etc, and even things like what material the CU should be made from.
TLC have extracts of Whitfield's book on their site:
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if you are contemplating work of this type you must have a copy of the on-site guide as a minimum:
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is also *tons* of information that has been written about in this group over the years - user google groups to search for it.
If you have an install in such a precarious state that the fuses regularly blow, yes it would be more convenient. However in that case there would be better things to spend the time & money on.
In practice it is more likely to cause inconvenience as MCBs are more liable to trip on filament bulb deaths.
I bought my house newly-built in 1969. It has re-wirable fuses and I have only had to repair one once - due to my overloading the lighting circuit with a 750 watt infra-red heater many years ago. No good reason for changing to anything else as far as I know.
One thing to watch with some of the plug in MCBs designed for old CUs is they tend to only have a 3kA breaking capacity. Unlikely to be a problem in most circumstances, however if you have a very low supply impedance they may be inadequate.
As I suggested, there is no real benefit. If someone cant cope with fuse wire once per decade, this isnt really the group for them, so I take it that isnt a problem..
What a waste of time. A quarter of the population dies through easily prevented causes, yet people spend thier energy solving imaginary problems.
There may not be a strong technical argument for replacing a rewireable CU with a MCB based one (many of the decision making factors are going to come down to the "human" issues rather than the technical), one thing you can probably say however is that the style of CU indicates and older installation. That may be an issue that does need addressing, since older installations frequently have rubber insulated cable being used way beyond its safe working life, insufficient sockets, tired accessories that no longer make clean contacts, lack of main or equipotential bonding, lack of RCD protection on socket circuits etc, or "whole house" RCD protection lacking discrimination.
If your ring main has a 1mm cpc instead of 1.5mm (as mine did), then it's okay with MCBs, but not fuses. I'd have to dig out my OSG to remind myself of the exact reason, but essentially in a fault current situaton the MCB will trip faster than the fuse (yes, I know that's not true for very large currents), thereby preventing the temperature in the cpc rising to the level where it can damage the insulation.
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